1. Field of the Invention
The invention relates to an optical memory.
2. Related Art
The function of "memory" is one of the key building blocks to implement advanced information processing in future ultrahigh-speed photonic networks. For example, memory allows 100 Gbit/s optical packets to be buffered and queued for subsequent processing of the data. Memory is also an intrinsic function for serial optical computing systems. Several types of serial optical memory have been demonstrated previously using recirculating optical fibre loops. These memory designs are either pulse-preserving, where the same optical pulses propagate on each circulation of the storage loop, or regenerative where the pulses are replaced after some number of memory circulations. For pulse preservation memories, the long term stability of the data pattern depends on being able to retime and reshape the optical pulses within the memory loop, since it acts like a long transmission line and the pulses are degraded by propagation effects. These effects are reduced by regenerative architectures which therefore offer superior stability. An all-optical regenerative memory is described in a paper entitled "All-optical regenerative memory", A. J. Poustie, K. J. Blow and R. J. Manning, Nonlinear Guided Waves and their Applications, Vol. 15, 1996 OSA Technical Digest Series, which has now been developed so that an optical pulse binary data pattern can be stored for several hours. This highly stable operation is achieved by full all-optical regeneration of the data pattern after each circulation of an optical fibre delay line. This all-optical memory design, shown in FIG. 1, is a combination of two nonlinear optical switching elements and an optical fibre storage loop.